Full: For 8 seconds, you take monumental damage that no living thing in Guild Wars could ever withstand. In return you are allowed to increase your attack speed just by a little bit, and the damage you deal in comparison to the damage you take is pathetic. If you haven't brought a cancel stance then you are officially screwed.
If you haven't brought a cancel stance at the time of activation of this skill, then you will recieve a fax stating that your are indeed officially screwed and that Arenanet cannot be held responsible for how generally impossible it is to survive the situation that you are in.
A general misconception is that attacking 33% faster makes you swing at 133% the normal rate. The increased number of swings is actually around 150%, see Flurry for details.